N‐heterocyclic carbene–palladium(II) complex supported on magnetic mesoporous silica for Heck cross‐coupling reaction

Magnetic mesoporous silica was prepared via embedding magnetite nanoparticles between channels of mesoporous silica (SBA‐15). The prepared composite (Fe₃O₄@SiO₂‐SBA) was then reacted with 3‐chloropropyltriethoxysilane, sodium imidazolide and 2‐bromopyridine to give 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐iumpropyl‐functionalized Fe₃O₄@SiO₂‐SBA as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica was further reacted with [PdCl₂(SMe₂)₂] to produce a supported N‐heterocyclic carbene–Pd(II) complex. The obtained catalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area measurement and X‐ray diffraction. The amount of the loaded complex was 80.3 mg g^?1, as calculated through thermogravimetric analysis. The formation of the ordered mesoporous structure of SBA‐15 was confirmed using low‐angle X‐ray diffraction and transmission electron microscopy. Also, X‐ray photoelectron spectroscopy confirmed the presence of the Pd(II) complex on the magnetic support. The prepared magnetic catalyst was then effectively used in the coupling reaction of olefins with aryl halides, i.e. the Heck reaction, in the presence of a base. The reaction parameters, such as solvent, base, temperature, amount of catalyst and reactant ratio, were optimized by choosing the coupling reaction of 1‐bromonaphthalene and styrene as a model Heck reaction. N‐Methylpyrrolidone as solvent, 0.25 mol% catalyst, K₂CO₃ as base, reaction temperature of 120°C and ultrasonication of the catalyst for 10 min before use provided the best conditions for the Heck cross‐coupling reaction. The best results were observed for aryl bromides and iodides while aryl chlorides were found to be less reactive. The catalyst exhibited noticeable stability and reusability.     

Regioselective synthesis of 1,4‐disubstituted triazoles using bis[(L)prolinato‐N,O]Zn complex as an efficient catalyst in water as a sole solvent

A concise, convenient and mild route for one‐pot regioselective synthesis of N‐aryl‐ and N‐alkyltriazoles in water as a sole solvent is reported. The methodology involves a three‐component reaction comprising aryl/alkyl‐alkyne, sodium azide and aryl/alkyl/allyl halide catalyzed by zinc(II) L ‐prolinate. Prominent features of our protocol are incorporation of transition metal catalyst other than copper, water as the reaction medium, recyclability of catalyst and avoidance of hazardous aryl azide as a reactant. Copyright © 2011 John Wiley & Sons, Ltd.     

有机-无机杂化材料负载的钯催化剂: 一种新型有效而可循环的无铜Sonogashira偶联反应

本文报道了有机-无机杂化材料固载的钯催化的无铜Sonogashira偶联反应。在3-[N,N-双（二苯基膦）氨基）]丙基功能化的硅胶固载的钯催化下,末端炔烃和碘代芳烃、溴代芳烃的偶联反应生成高产率相应的偶联产物。反应条件包括使用乙二醇为溶剂,三乙胺为碱。而且硅胶负载的膦钯催化剂和溶剂乙二醇经简单处理,可循环使用6次不降低活性。     

Chiral Ammonium Betaine‐Catalyzed Highly Stereoselective Aza‐Henry Reaction of α‐Aryl Nitromethanes with Aromatic N‐Boc Imines

A highly stereoselective aza‐Henry reaction of α‐aryl nitromethanes with aromatic N‐Boc imines was established by using C₁‐symmetric chiral ammonium betaine as a bifunctional organic base catalyst. Various substituted aryl groups for both imines and nitromethanes were tolerated in the reaction, and a series of precursors for the synthesis of unsymmetrical anti‐1,2‐diaryl ethylenediamines was provided.     

A Transformation of N‐Alkylated Anilines to N‐Aryloxamates

Transformation of N‐alkylated anilines to N‐aryloxamates was studied using ethyl 2‐diazoacetoacetate as an alkylating agent and dirhodium tetraacetate (Rh₂(OAc)₄) as the catalyst. The general applicability of the reaction as a synthetic method for N‐aryloxamates was studied with a number of substituted N‐alkylated anilines. The results revealed that the oxamate was formed by a radical reaction with molecular O₂ and Rh₂(OAc)₄ as initiator.     

N‐Heterocyclic carbene/phosphite synergistically assisted Pd/C‐catalyzed Suzuki coupling of aryl chlorides

An N‐heterocyclic carbene and phosphite synergistically enhanced Pd/C catalyst system has been developed for Suzuki coupling of aryl chlorides and aryl boronic acids from commercially available Pd/C with sterically demanding N,N′‐bis(2,6‐diisopropylphenyl)imidazolylidene and trimethylphosphite. A remarkable increase in catalytic activity of Pd/C was observed when used along with 1 equiv. N,N′‐bis(2,6‐diisopropylphenyl)imidazolium chloride and 2 equiv. phosphite with respect to palladium in appropriate solvents that were found to play a crucial role in Pd/C‐NHC‐P(OR)₃‐catalyzed Suzuki coupling. A dramatic ortho‐substitution effect of carbonyl and nitrile groups in aryl chlorides was observed and explained by a modified quasi‐heterogeneous catalysis mechanism. The Pd/C catalyst could be easily recovered from reaction mixtures by simple filtration and only low palladium contamination was detected in the biparyl products. A practical process for the synthesis of 4‐biphenylcarbonitrile has therefore been developed using the N‐heterocyclic carbene/phosphite‐assisted Pd/C‐catalyzed Suzuki coupling. Copyright © 2013 John Wiley & Sons, Ltd.     

An Efficient One‐Pot Synthesis of 7,7‐Dimethyl‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐4‐aryl‐7,8‐dihydroquinolin‐5(6H)‐one Derivatives Using Chitosan–SO3H as Biodegradable Organocatalyst

Chitosan sulfonic acid (CS–SO₃H), a biodegradable green catalyst, was found to be an impressive system for one‐pot four‐component reaction of different aromatic aldehydes, 3‐acetylcoumarin, dimedone, and ammonium acetate leading to 7,7‐dimethyl‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐4‐aryl‐7,8‐dihydroquinolin‐5(6H)‐one under solvent‐free condition. This methodology produces diverse superiorities such as operational simplicity, short reaction time, and high yield. Further, the catalyst can be reused for four times without any noticeable decrease in the catalytic activity.     

Nickel‐Catalyzed Synthesis of N‐Aryl‐1,2‐dihydropyridines by [2+2+2] Cycloaddition of Imines with Alkynes through T‐Shaped 14‐Electron Aza‐Nickelacycle Key Intermediates

Despite there being a straightforward approach for the synthesis of 1,2‐dihydropyridines, the transition‐metal‐catalyzed [2+2+2] cycloaddition reaction of imines with alkynes has been achieved only with imines containing an N‐sulfonyl or ‐pyridyl group. Considering the importance of 1,2‐dihydropyridines as useful intermediates in the preparation of a wide range of valuable organic molecules, it would be very worthwhile to provide novel strategies to expand the scope of imines. Herein we report a successful expansion of the scope of imines in nickel‐catalyzed [2+2+2] cycloaddition reactions with alkynes. In the presence of a nickel(0)/PCy₃ catalyst, a reaction with N‐benzylidene‐P,P‐diphenylphosphinic amide was developed. Moreover, an application of N‐aryl imines to the reaction was also achieved by adopting N‐heterocyclic carbene ligands. The isolation of an (η²‐N‐aryl imine)nickel(0) complex containing a 14‐electron nickel(0) center and a T‐shaped 14‐electron five‐membered aza‐nickelacycle is shown. These would be considered as key intermediates of the reaction. The structure of these complexes was unambiguously determined by NMR spectroscopy and X‐ray analyses.     

Studies on the reactivity of some N‐aryl‐ and N‐heteroaryl‐N'‐alkylthioureas towards electrophilic reagents. Synthesis of new N‐pyridylthioureas and thiazolines maría

Here in we describe our findings about the behaviour of some N‐aryl‐ and N‐heteroaryl‐N'‐alkylthioureas towards electrophilic reagents. In acid medium, the treatment of thioureas bearing aryl groups with 4‐chloropyridine in 2‐propanol yielded N‐aryl‐N‐(4‐pyridyl)‐N'‐alk;ylthioureas and N‐aryl‐N'‐alkylureas, whereas the heteroarylthioureas tested under similar reaction conditions afforded N‐heteroaryl‐N'‐alkyl‐O‐(2‐propyl)isoureas. The reaction of N‐(5,6,7,8‐tetrahydronaphth‐1‐yl)‐ and N‐(2‐benzimidazolyl)‐N'‐butyl‐thiourea with propargyl bromide in acid medium led to the formation of 2‐butylimino‐3‐arylthiazolines, in a regioselective way. However, when this reaction was carried out in basic conditions the regioselectivity failed and a mixture of isomeric thiazolines was obtained. The Z‐ or E‐configuration of the imino group of the synthesized thiazolines was studied by molecular modelling and by selective nuclear Overhauser experiments in nuclear magnetic resonance.     

CuI/8‐Hydroxyquinalidine Promoted N‐Arylation of Indole and Azoles

An efficient catalytic system of CuI/8‐hydroxyquinalidine was developed for the coupling of aryl iodides and indole as well as some azoles. The reaction could be carried out at 90°C under the condition of relatively low catalyst loading, affording various N‐arylindoles and N‐aryl azoles in good yields. The functionalized and hindered aryl iodides were suitable substrates for this transformation.     

Copper‐Catalyzed Asymmetric Arylation of N‐Heteroaryl Aldimines: Elementary Step of a 1,4‐Insertion

Copper complexes of monodentate phosphoramidites efficiently promote asymmetric arylation of N‐azaaryl aldimines with arylboroxines. DFT calculations and experiments support an elementary step of 1,4‐insertion in the reaction pathway, a step in which an aryl‐copper species adds directly across four atoms of C=N?C=N in the N‐azaaryl aldimines.     

Efficient and Green Synthesis of N‐aryl Pyrroles Catalyzed by Ionic Liquid [H‐NMP][HSO4] in Water at Room Temperature

A suitable and efficient method for the synthesis of N‐aryl pyrroles by using 2,5‐dimethoxy tetrahydrofuran and several primary aromatic amines in the presence of the catalytic amount of [H‐NMP][HSO₄] under room temperature was described. This method has the advantages such as; easy reaction workup, absolutely separated of catalyst from the reaction mixture and smoothly recyclability of catalyst. In this reaction, N‐substituted pyrroles were obtained as desired products in excellent yields and short reaction times via green and one‐pot procedure.     

A New Route to N‐Aryl 2‐Alkenamides,N‐Allyl N‐Aryl 2‐Alkenamides,and N‐Aryl α,β‐Unsaturated γ‐Lactams from N‐Aryl 3‐(Phenylsulfonyl)propanamides

A series of N‐aryl 2‐alkenamides were produced efficiently by treating N‐aryl 3‐(phenylsulfonyl)‐propanamides with potassium tert‐butoxide in THF at 0°C. With out isolation, it was further treated with an additional equivalent of potassium tert‐butoxide and allyl bromide to give N‐allyl N‐aryl 2‐alkenamides in one pot in good yields. Followed by a ring‐closing metathesis reaction, these N‐allyl N‐aryl 2‐alkenamides were respectively converted into corresponding N‐aryl α,β‐unsaturated γ‐lactams in moderate yields.     

An Efficient N‐Arylation of Heterocycles with Aryl‐, Heteroaryl‐, and Vinylboronic Acids Catalyzed by Copper Fluorapatite

N‐Arylation of N‐containing heterocycles, such as pyrazoles, imidazoles, and benzimidazoles with aryl‐, heteroaryl‐, and vinylboronic acids was efficiently carried out by copper fluorapatite (CuFAP) catalyst in MeOH at room temperature under base‐free conditions. The N‐arylated heterocycles were isolated in good‐to‐excellent yields.     

A Mild and Efficient Method for N‐Arylnucleobase Synthesis via the Cross‐Coupling Reactions of Nucleobases with Arylboronic Acids Catalyzed by Simple Copper Salts

A simple and efficient copper‐salt catalyzed N‐arylation of nucleobases is reported. In a mixed solvent of MeOH and H₂O, the coupling products were obtained in moderate to excellent yields at room temperature within a short time. A variety of substituted N‐aryl nucleobases can be prepared through this procedure.     

Ligand‐free CuTC‐catalyzed N‐arylation of amides,anilines and 4‐aminoantipyrine: synthesis of N‐arylacrylamides, 4‐amido‐N‐phenylbenzamides and 4‐amino(N‐phenyl)antipyrenes

N‐Arylation of amides and anilines with aryl iodides was efficiently catalyzed by copper thiophenecarboxylate under ligand‐free conditions with good to excellent yields. A variety of substituted aryl iodides, amides, anilines and 4‐aminoantipyrine were found to be applicable to the simple catalytic system. Furthermore, some practical, unique secondary amides, such as N‐arylacrylamides and 4‐amido‐N‐phenylbenzamides, and 4‐amino(N‐phenyl)antipyrenes, which are difficult to obtain by the classical methods, were prepared. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium‐catalyzed Suzuki–Miyaura coupling with aryl and heteroaryl bromides using N,N,N′,N′‐tetra(diphenylphosphinomethyl)‐1,2‐ethylenediamine

An easily prepared tetraphosphine N,N,N′,N′‐tetra(diphenylphosphinomethyl)‐1,2‐ethylenediamine (1) combined with PdCl₂ affords an efficient catalytic system for Suzuki cross‐coupling of aryl and heteroaryl bromides. A high turnover number of 750 000 is obtained with the catalyst loading as low as 1 ppm. This catalyst system exhibits good stability and longevity. In this study, a broad scope of substrates is investigated and satisfactory yields are obtained. Copyright © 2012 John Wiley & Sons, Ltd.     

SBA‐15‐functionalized melamine–pyridine group‐supported palladium(0) as an efficient heterogeneous and recyclable nanocatalyst for N‐arylation of indoles through Ullmann‐type coupling reactions

SBA‐15‐functionalized melamine–pyridine group‐supported palladium(0) was found to serve as a heterogeneous and recyclable nanocatalyst for N‐arylation of indoles with aryl iodides under a low catalyst loading (0.3 mol% of Pd) through Ullmann‐type C? N coupling reactions. A variety of aryl iodides could be aminated to provide the N‐arylated products in good to excellent yields without the need of an inert atmosphere. Also, this catalyst was found to be an efficient system for the N‐arylation of other nitrogen‐containing heterocycles with aryl iodides. The heterogeneous palladium catalyst could be recovered by simple filtration of the reaction solution and reused for six cycles without significant loss in its activity. Copyright © 2015 John Wiley & Sons, Ltd.     

An Exceedingly Mild,Green Synthesis of Substituted N‐3‐diaryl‐1,8‐naphthyridin‐2‐amine Derivatives and Their Antimicrobial Activity

An exceedingly and highly efficient procedure has been described for the synthesis of substituted N‐3‐diaryl‐1,8‐naphthyridin‐2‐amines by the reaction of 2‐chloro‐3‐aryl‐1,8‐naphthyridines with various anilines in the presence of N‐methyl‐2‐pyrrolidone and K₂CO₃ under thermal green solvent‐free conditions. The significant features of this green reaction include very good yields in purity, simple experimental, short reaction time, easy workability, and avoidance of toxic solvents. All synthesized compounds have been evaluated for their antibacterial activity.     

Pd‐SBT@MCM‐41: As an efficient,stable and recyclable organometallic catalyst for C‐C coupling reactions and synthesis of 5‐substituted tetrazoles

A palladium S‐benzylisothiourea complex was anchored on functionalized MCM‐41 (Pd‐SBT@MCM‐41) and applied as efficient and reusable catalyst for the synthesis of 5‐substituted 1H –tetrazoles using [2 + 3] cycloaddition reaction of various organic nitriles with sodium azide (NaN₃) in poly(ethylene glycol) (PEG) as green solvent. Also this catalyst was applied as an versatile organometallic catalyst for Suzuki cross‐coupling reaction of aryl halides and phenylboronic acid (PhB(OH)₂) or sodium tetraphenyl borate (NaB(Ph)₄). This nanocatalyst was characterized by thermal gravimetric analysis (TGA), X‐ray Diffraction (XRD), scanning electron microscopy (SEM), inductively Coupled Plasma (ICP) and N₂ adsorption–desorption isotherms techniques. Recovery of the catalyst is easily achieved by centrifugation for several consecutive runs.